This invention relates to a method for determining the distribution of a coating composition on a carpet structure.
In the production of carpets such as carpets of the tufted type wherein a plurality of loops of yarn are deposited in a primary backing material, the back surface is generally coated with a binder composition, e.g., a natural or synthetic latex composition or like material. This binder composition imparts to the carpet structure desired physical properties such as anchorage of the carpet yarns and dimensional stability.
In a typical operation, the application of such binder generally comprises transferring the liquid binder composition from an applicator roll which rotates in a bath of said composition to the back side of a carpet structure passing across the top of said rolls. The carpet backing is then exposed to a scraper blade and, optionally, a lick roll, which removes any excess composition which may have been applied. A secondary backing, generally referred to as secondary jute, is then married to the coated carpet and the carpet passed through an oven to dry and/or cure the binder.
In the application process, the quantity of binder applied to the carpet is advantageously that minimum amount required to impart the desired properties to the carpet following the curing and/or drying thereof. To achieve the maximum benefits from such amounts of binder, it is desirable to control its distribution. For example, it is often advantageous to distribute the binder such that prior to the marriage with the secondary jute the primary backing material and carpet yarns exposed on the backing, e.g., loops or tufts, are substantially covered and there is essentially no penetration of the binder to the carpet facing. See, for example, The Application of Synthetic Resin Emulsions by H. Warson, published in 1972 by Ernest Benn Limited, London, Chapter X, "Miscellaneous Textile Applications."
Unfortunately, small variations in the application process, e.g., viscosity of the liquid binder composition and pressures exerted by the scraper blade or lick roll, will often cause significant fluctuations in the distribution of the binder on the carpet. Thus, in a normal application process, although identical amounts of binder are applied, the distribution of the binder may vary significantly. Often, due to this variation in distribution, the properties and performance of the resulting carpet are non-uniform.
Heretofore, the distribution of the binder on the back side of the carpet structure has been determined by visual inspection. Unfortunately, such method is inherently inaccurate, not uniformly reproducible, and requires extensive amounts of time. As such, process changes cannot readily be made to correct undesirable distributions of the coating.
In view of the stated deficiencies of the conventional methods for determining the distribution of the coating composition on a carpet structure, it would be highly desirable to provide a method for efficiently determining said distribution.